Tuesday, 10 June 2014

The nature of the Nathdwara Meteorite.

On 25 December 2012 at about 6.20 pm local time a single meteorite fell in a field near the town of Nathdwara in southern Rajastan. The meteorite was an oblong shape, 12 cm along its longest axis, and weighed about 1.5 kg. It was covered by a dark fusion crust, formed by melting of its outer surfaces by friction as it passed through the atmosphere, and when broken apart by local villagers the interior was found to be a grey rocky material.

Original piece after it was collected by the villagers and was slightly broken at top; the diameter of the meteorite piece is about 3 cm, and the length is about 12 cm. Agarwal et al. (2014).

Argawal et al. were able to examine a 30g piece of the Nathdwara Meteorite. This was a chondrite (stoney meteorite) with a largely re-crystalized structure, showing some relict chondrules (spherical mineral grains found in meteorites, thought to have formed from the cooling of molten droplets of minerals in space before the accretion of the material into a meteorite). Mineral grains of olivine, pyroxene and feldspar could be seen in thin section, as could considerable amounts of troilite (an iron sulphide mineral). The meteorite was found to comprise 29.2 % iron by weight, making it an H Chondrite (High iron Chondrite), and its re-crystalized mineralogy leads Argawal et al. to classify it further as an H6 Chondrite (High iron Chondrite with largely re-crystalized chondrules).

(a) Photomicrographs of the thin section of the Nathdwara meteorite under plane polarized light, the scale is given showing the mineral assemblages and the matrix of the meteorite sample (various minerals are indicated as Ole-olivine, Cpxe-clinopyroxene, Troe-troilite, Sple-spinel, and Ilme-ilmenite). (b) Relict skeletal olivine chondrule, and pyroxene. Nicols crossed, porphyritic olivine integrating with the matrix. Agarwal et al. (2014).

On 28 February 2010 a meteor shower fell over Slovakia, accompanied by a bright fireball and a series of sonic booms. Subsequently a number of meteorites were recovered from the area to the northwest of the city of Košice, in the east of the country, most within four weeks of the observed shower (meteors are ‘shooting stars’ observed in the sky, a meteorite is an actual piece of rock of presumed extra-terrestrial origin).

Lake Bosumtwi is an 8 km diameter roughly circular lake about 30 km to the southeast of Kumasi in the Ashanti Province of Ghana. It is thought to have been created by a large meteorite impacting the Earth roughly 1.07 million years ago during the Late Pleistocene; the impact crater being roughly 10.5 km in diameter, with the lake...

No comments:

Post a Comment

About Me

Studied Palaeobiology & Evolution at the University of Portsmouth, Geosciences via the Open University & Ecology and Conservation at Christchurch University, Canterbury.
Have worked in wildlife based tourism, mineral exploration, development, conservation, education & environmental chemistry. Occasionally write articles for papers and magazines.

This Blog would be impossible without the work of countless scientists (and others) throughout the world. Where possible I do my best to credit them, but there will always be many more who remain unmentioned; this does not imply I am ungrateful for their contributions. Any errors or inaccuracies are, of course, my own.